1. Field of the Invention
The present invention relates to a liquid ejecting apparatus, and more particularly to a liquid ejecting apparatus which attaches liquid ejected from orifices of a nozzle plate mounted in a liquid ejecting head to a recording object.
2. Description of the Related Art
In liquid ejecting apparatuses, when attaching liquid to the entire area of a recording object leaving no margin uncovered with the liquid near the edges of the recording object, the liquid is ejected to over a slightly wider area than the dimension of the recording object, considering inevitable misalignment between the recording object and the liquid ejecting head. Accordingly, the liquid is also ejected to a region where the recording object is not present, which is near the side edges and the upper and lower edges of the recording object. Accordingly, an absorbing member is disposed outside the recording object at a position facing the liquid ejecting head so as to absorb the remainder of the liquid which is ejected from the liquid ejecting head but not attached to the recording object. With such a structure, it is possible to prevent outskirts of the recording object from being smudged by the remainder of the liquid which is not attached to the recording object.
By the way, when the liquid is attached to the recording object, a portion of the recording object, to which the liquid is attached, is apt to expand and to thereby wrinkle. If wrinkles come into contact with the absorbing member, the liquid absorbed in the absorbing member may contaminate the recording object. Accordingly, in a number of liquid ejecting apparatuses, a gap of 2 to 4 mm is provided between the recording object and the absorbing member, considering the height of the wrinkles of the recording object. In similar manner, in order to prevent the recording object from being smudged due to the contact between the wrinkles of the recording object and the absorbing medium, a gap of 1 mm is provided between the nozzle plate and the recording object. Accordingly, in total, a gap of 3 to 5 mm is provided between the nozzle plate and the absorbing member.
On the other hand, on purpose to enhance resolution of an image formed on the recording object by attaching the liquid to the recording object, liquid droplets are ejected from orifices of the nozzle plate is atomized further. A single liquid droplet has a size of several pl. Since each of such minute liquid droplets has very a small mass, the liquid droplets rapidly lose their kinetic energy due to viscous resistance of ambient gas after they are ejected from the nozzle plate. For example, after liquid droplets each having a size smaller than 8 pl travel a distance of about 3 mm in the air, flight velocity of the liquid droplets decreases to almost zero. It takes a long period for the minute liquid droplets that completely lost their kinetic energy to fall to a target position because the falling motion attributable to the gravitational acceleration and the viscous resistance of ambient are balanced. The liquid droplets suspending in the air until they arrive at the target position is called aerosol.
Some of the aerosol produced in such a manner escapes from the liquid ejecting apparatus, suspending away outward and then sticks to objects in surroundings. On the other hand, most of the aerosol sticks to elements in the liquid ejecting apparatus. In the case in which the aerosol sticks to a transportation path of the recording object, such as platen, succeeding recording objects become contaminated due to reattaching of the aerosol. In the case in which the aerosol is attached to electric circuits, linear scales, rotary encoders, optical sensors, and the like mounted in the liquid ejecting apparatus, the attachment of aerosol brings about device malfunction. In addition, if a user touches a spot to which the aerosol is attached, the user's hand gets stained.
Patent document 1 discloses a liquid ejecting apparatus having a function of actively collecting aerosol using an electric field. In the liquid ejecting apparatus disclosed in the document, an absorbing member is arranged in a position facing a nozzle plate on purpose to attract and absorb the remainder of the liquid droplets which is not attached to the recording object. A metal member serving as one electrode is arranged close to the absorbing member and the nozzle plate made of a metal and provided with orifices, from which liquid is ejected, serves as a counter electrode.
If different voltages are applied to the electrode and the nozzle plate, respectively, an electric field is generated between them. On the other hand, liquid droplets ejected from the nozzle plate are electrified to have the same polarity as the nozzle plate due to lighting rod effect as soon as the liquid droplets are ejected from the nozzle plate. Accordingly, minute liquid droplets which can become aerosol continuously fly toward the electrode without velocity loss thanks to Coulomb force generated by the electric field, and are then attached to the electrode having the reverse polarity. Further, the liquid droplets attached to the electrode are absorbed by the absorbing member arranged close to the electrode by capillarity.    Patent Document: JP-A-2004-202867